"Hitotsu" has more than one meaning. The root of the word, "hito" means roughly "one"/"first", and this corresponds with the various meanings hitotsu can have, depending on how it is used.
It is a counter for the number one.
It can mean "one [of something]."
It can be used for the beginning/start of something(because of it's "1" connotation, of course).
At the beginning of a sentence, it's meaning is akin to "for one thing", "first off", etc..
Once you get the general implication of the word, it's various uses will all begin to make sense, and you will be able to understand it's exact meaning by logical deduction, depending on the context you find it in.
Kami no hitotsu no kazoku
You may say 'hitotsu wo toru.'
futatsu wa hitotsu ni naru
一つの大きな Hitotsu no ōkina
"Ichi" (一). Or, if you're referring to one object, "hitotsu" (一つ).
'Wastashi no ikimono WA hitotsu chiisana ha wo motteimasu.'
You may say 'ooku no hitotsu,' written: 多くの一つ
Hitotsu was created on 2008-03-05.
'Sore shika daisuki ni narimasen tatta hitotsu no kurabu'.
1つの色のみ hitotsu no iro nomi
orenji wo tabette ii desuka for eat orenji hitotsu onegaishimasu if your asking to buy it
Tatta Hitotsu no Omoi was created on 2008-01-23.